6. Where a certificate of eligibility has been issued for the brother or sister of a child for whom a request is made under paragraph 1, 2, 3 or 5 of section 73 of the Charter, the eligibility of that child may be demonstrated by producing that certificate of eligibility or a certified true copy thereof and the birth certificate of the child’s brother or sister stating the names of their father and mother. Failing such certificate, any other official document issued by a competent authority and establishing the date of birth, sex and filiation of the child shall be produced.